A379452 Number of compositions (ordered partitions) of 1 into n distinct reciprocals of positive integers.

1, 0, 6, 144, 8640, 1670400, 1238655600, 6095673521280

Offset

1,3

Links

Table of n, a(n) for n=1..8.

Formula

a(n) = n! * A006585(n).

Example

a(3) = 6 because we have 1 = 1/2 + 1/3 + 1/6
                           = 1/2 + 1/6 + 1/3
                           = 1/3 + 1/2 + 1/6
                           = 1/3 + 1/6 + 1/2
                           = 1/6 + 1/2 + 1/3
                           = 1/6 + 1/3 + 1/2.

Crossrefs

Cf. A002966, A002967, A006585.

Sequence in context: A085905 A203978 A090443 * A307416 A133460 A166953

Adjacent sequences: A379449 A379450 A379451 * A379453 A379454 A379455

Keyword

nonn,hard,more

Author

Ilya Gutkovskiy, Dec 23 2024

Status

approved